/*
 * jPOS Project [http://jpos.org]
 * Copyright (C) 2000-2015 Alejandro P. Revilla
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.jpos.iso;


/**
 * EbcdicPrefixer constructs a prefix for EBCDIC messages.
 *
 * @author joconnor
 * @version $Revision$ $Date$
 */
public class EbcdicPrefixer implements Prefixer {
	/**
	 * A length prefixer for upto 99 chars. The length is encoded with 2 EBCDIC
	 * chars representing 2 decimal digits.
	 */
	public static final EbcdicPrefixer LL = new EbcdicPrefixer(2);
	/**
	 * A length prefixer for upto 999 chars. The length is encoded with 3 EBCDIC
	 * chars representing 3 decimal digits.
	 */
	public static final EbcdicPrefixer LLL = new EbcdicPrefixer(3);
	/**
	 * A length prefixer for upto 9999 chars. The length is encoded with 4
	 * EBCDIC chars representing 4 decimal digits.
	 */
	public static final EbcdicPrefixer LLLL = new EbcdicPrefixer(4);

	private static byte[] EBCDIC_DIGITS = {(byte) 0xF0, (byte) 0xF1, (byte) 0xF2,
			(byte) 0xF3, (byte) 0xF4, (byte) 0xF5, (byte) 0xF6, (byte) 0xF7, (byte) 0xF8,
			(byte) 0xF9};

	/**
	 * The number of digits allowed to express the length
	 */
	private int nDigits;

	public EbcdicPrefixer(int nDigits) {
		this.nDigits = nDigits;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.jpos.iso.Prefixer#encodeLength(int, byte[])
	 */
	public void encodeLength(int length, byte[] b) {
		for (int i = nDigits - 1; i >= 0; i--) {
			b[i] = EBCDIC_DIGITS[length % 10];
			length /= 10;
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.jpos.iso.Prefixer#decodeLength(byte[], int)
	 */
	public int decodeLength(byte[] b, int offset) {
		int len = 0;
		for (int i = 0; i < nDigits; i++) {
			len = len * 10 + (b[offset + i] & 0x0F);
		}
		return len;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.jpos.iso.Prefixer#getLengthInBytes()
	 */
	public int getPackedLength() {
		return nDigits;
	}
}